(a) Field of the Invention
The present invention relates to a switch control device and a converter including the same. In particular, the present invention relates to a switch control device for safely controlling a converter when information of an input voltage of a converter is not input to the switch control device, and a converter including the same.
(b) Description of the Related Art
FIG. 1 equivalently shows a converter. The converter includes an inductor 900, a switch 901, a diode 902, and a capacitor 903. An inductor current iL flows through the inductor 900 according to an input voltage Vin, the capacitor 903 is charged by the inductor current iL, and a charged voltage at the capacitor 903 becomes an output voltage of the converter. When the switch 901 is in the turn-on state and the diode 902 is in the turn-off state, the inductor current iL is increased with the passage of time and the inductor 900 stores energy. When the switch 901 is turned off and the diode is turned on, the inductor current iL passing through the diode 902 charges the capacitor 903. In this instance, the energy stored in the inductor 900 is transmitted to the capacitor 903 and the inductor current iL is reduced with the passage of time.
The conventional controller controls an operation of the convertor during a predetermined period even though the input voltage is not input to the converter. The controller controls an operation of the converter during a period or two periods of the input AC voltage without the input voltage. Then, it makes the output voltage be reduced that there is no input voltage, even though the converter is normally operating. The controller controls the converter to operate with a maximum gain in order to compensate for the decreasing output voltage. A switching frequency of the converter must be a minimum and a duty of the switching must be a maximum for the converter to operate at the maximum gain.
When the input AC voltage is again input to the converter operating according to the maximum gain, since the switching is operated according to the maximum duty, a peak value of a current flowing through the switch is suddenly increased.
The present invention has been made in an effort to provide a switch control device and a converter including the same having advantages of controlling a converter when information of an input voltage is not input to a controller controlling a converter. When a converter is operated at a maximum gain without an input voltage and then an input AC voltage is input to the converter, a large current is generated to the converter operated at the maximum gain. A configuration (e.g., a switching element of a converter, etc) of the converter is damaged by the large generated current. Particularly, during an operation of the converter, when a blackout is generated at the moment or after the input voltage is unstable and a low voltage is applied, when the input AC voltage is recovered, a switch current is sharply increased, and hence, because of damage to the converter and the sharp increase of the switch current, an interruption is generated in a soft start operation.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.